1. Field
This disclosure relates to the field of audio signal processing.
2. Background
Coding schemes based on the modified discrete cosine transform (MDCT) are typically used for coding generalized audio signals, which may include speech and/or non-speech content, such as music. Examples of existing audio codecs that use MDCT coding include MPEG-1 Audio Layer 3 (MP3), Dolby Digital (Dolby Labs., London, UK; also called AC-3 and standardized as ATSC A/52), Vorbis (Xiph.Org Foundation, Somerville, Mass.), Windows Media Audio (WMA, Microsoft Corp., Redmond, Wash.), Adaptive Transform Acoustic Coding (ATRAC, Sony Corp., Tokyo, JP), and Advanced Audio Coding (AAC, as standardized most recently in ISO/IEC 14496-3:2009). MDCT coding is also a component of some telecommunications standards, such as Enhanced Variable Rate Codec (EVRC, as standardized in 3rd Generation Partnership Project 2 (3GPP2) document C.S0014-D v2.0, Jan. 25, 2010). The G.718 codec (“Frame error robust narrowband and wideband embedded variable bit-rate coding of speech and audio from 8-32 kbit/s,” Telecommunication Standardization Sector (ITU-T), Geneva, CH, June 2008, corrected November 2008 and August 2009, amended March 2009 and March 2010) is one example of a multi-layer codec that uses MDCT coding.